A Novel Cable Actuation Mechanism for 2-DOF Hyper-redundant Bending Robot Composed of Pulleyless Rolling Joints

Many surgical robots are remotely actuated by means of wire cables. In the past, the cables wound around circular pulleys at the robot joints did not constitute a problem of the cable driver structure. However, the pulleys inside the joints are removed recently in order to miniaturize the joints, so a specially designed cable driver suitable for the miniature joint structure is required for stable driving. In this paper, we propose a novel cable driver design for driving a pulleyless rolling joint and extend it to 2-DOF structure. Then, the proposed cable driver is manufactured using 3D printing with the 2-DOF bending joint, and an experiment is performed to evaluate them using the prototype. The cable driver proposed in this paper can drive pulleyless rolling joints stably with low cable tension. In addition, it can decouple yaw and pitch motion of the joints completely, therefore it can be applied to a variety of thin robots and instruments including steerable endoscopes and surgical robots.